How many eggs should chickens lay per day???

I am a bit confused. I have 4 average sized chickens in my back yard. They have the run of the yard which is about 400sqm. Recently they have started laying lots of eggs. Sunday afternoon i went down and collected 8 eggs from there nest which i thought is quite a lot as they usually only have 4-5 per day but then 2 days later when i went to collect the eggs there were 13. Every one i ask has said not possible, they could not lay that many so i wonder am i getting egg fairies??? They are nesting so does this make them lay more??

My chickens coop is totally inclosed. And they always lay in the exact same spot. They have been getting lots of food lately. My husband is a chef so they get all his scraps from work (not chicken though). Does diet affect egg laying?

Monday (morning) you collect 4 eggs thinking they were laid that day, but they were all actually laid the day before, after you had already checked the nest.
Monday (later that day) 4 eggs are laid, so the nest now contains 4.
Tuesday you don't collect eggs, and they lay another 4. The nest now contains 8.
Wednesday they lay another 4 eggs. The nest now contains 12 eggs ready for when you collect them.

These might not be the actual days or numbers, but can you see where I'm going with this? It is possible to have an empty nest one day, and 12 eggs two days later, from only 4 chooks. My girls quite regularly lay in the afternoons, long after I've given up waiting for my breakfast/lunch omelet.

Monday (morning) you collect 4 eggs thinking they were laid that day, but they were all actually laid the day before, after you had already checked the nest.
Monday (later that day) 4 eggs are laid, so the nest now contains 4.
Tuesday you don't collect eggs, and they lay another 4. The nest now contains 8.
Wednesday they lay another 4 eggs. The nest now contains 12 eggs ready for when you collect them.

These might not be the actual days or numbers, but can you see where I'm going with this? It is possible to have an empty nest one day, and 12 eggs two days later, from only 4 chooks. My girls quite regularly lay in the afternoons, long after I've given up waiting for my breakfast/lunch omelet.

That seems entirely more likely. We have had hens lay as late as 4:30 pm local time, especially when they are first starting.

I think a lot about this (obvious reasons!) Couldn't this be similar to a woman releasing two eggs instead of one in the same month, thus resulting in twins? I got 5 eggs today from 4 hens. I only had 3 and 4 the last couple days, but 6 and 7 before that.

Look at this, "When I was in high school I worked on a "egg ranch". We had 160,000 chickens and monitored the output of each hen daily. The chickens were fed a "laying mash" which induced them to produce high quality eggs at the fastest rate possible. We also used lighting as an inducement, as mnemosyne pointed out earlier. The desired results were to have every hen lay one egg a day, every day. Having a hen lay two in a day wasn't too uncommon though, but three was rare. I don't recall any hen laying multiple eggs per day consistantly." http://boards.straightdope.com/sdmb/archive/index.php/t-167011.html